225 or 235

Messages
702
Location
Midland, MI
I am getting some new tires and have a question and I am looking for your opinions. The stock tires are 215/75/15 tires, but I was thinking I would like a little taller sidewall so the guy at the tire store gave me a price on some 235's. I got to looking at the product sheets and for every jump of ten in aspect ratio the diameter of the tire increases 0.60 inches. The problem is when I looked at the weight of the tires from 215 to 225 to 235 the weight jumps dramatically from 225 to 235, not so from 215 to 225. I am jumping more than 2 pounds per tire going from 215 to 235, and only .6 pounds more going from 215 to 225. Any reason why I should go with the extra weight and additional height over the 225, or do you think the 225 would be a good compromise?
 
Messages
780
Location
Palatine IL
What's your wheel width and aspect ratio. Usually you can go up 1 size (up to 3%) without worries with the same profile. More than that will often not be optimal for the wheel width and but still fit. You won't handle as well because the sidewall will lose support.
 
Messages
12,385
Location
Northern CA
quote:
Originally posted by novadude: Don't forget that a larger tire will throw off your speedometet/odometer too.
Speedometers tend to read a bit high from the factory, one size up sometimes makes them more accurate. It's worked for me more than once. In my case it also made the odometers more accurate. YMMV [Big Grin]
 
Messages
1,910
Location
Vista, CA
The larger mass might lower your gas mileage just a little tiny bit. A larger tire won't always gain you mileage as if often thought. The larger tire has greater mass to get moving and more drag and rolling resistance. If the new tire raises your car just a tiny bit it will also change your scrub radius in the front suspension. If you car is designed to have a bit of negative scrub radius and you increase it or decrease it you will effect the braking, especially in panic stops or braking while turning. If you have a front wheel drive car you get the fun of slightly different braking along with different dynamics any time you step on the gas. If you don't care about the dynamic behavior supplied by the original design then go for the bigger tires. Who knows, maybe a change won't be noticed. Ask your tire guy about suggestions for new caster setting to compensate for a scrub radius change. Also ask if the larger tire will add to any already existing bump steer in you car. He might even suggest a ride height change to restore the anti-dive/squat geometry. A half inch may be all you need to get started. Or you can just put the correct size tire back on go monkey with something else. There is a lot of though and work in your car's design that you may not appreciate and tires are kind of important. I'd consider keeping the same size tire.
 
Messages
1,627
Location
Timberline
1st off, what kind of vehicle? If it's a truck, 1 or 2 sizes is not any big deal, I've had several trucks in which I've put on 1 size bigger. If anything, it gave me more ground clearance and most of the time, a softer ride - more sidewall. If it's a car, I don't know if I would change anything - car's are not designed to having their diameter's altered, trucks are different. If you're talking a minivan, we recently did this with my sister's - she had 195/75 14's which she wore 3 sets out in less then a 2-yr period. Discount tire suggested it was because the tires were just flat too skinny for the shape/design of the vehicle. They recently installed 205/70's - she LOVES them, it's a "whole new ride."
 
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